Method for splicing a conveyor belt

ABSTRACT

A method is provided for splicing a conveyor belt having vulcanized rubber with steel strands embedded in the vulcanized rubber, comprising the steps of exposing a plurality of strands at two belt ends, and applying a vulcanizable rubber composition to the exposed strands to form a spliced joint between the two belt ends, the vulcanizable rubber composition comprising 100 parts by weight of rubber, and the rubber comprising from about 1 to about 40 parts by weight of a polyoctenamer.

FIELD OF THE INVENTION

[0001] The invention is directed to a method for splicing a conveyorbelt having vulcanized rubber with steel strands embedded in thevulcanized rubber, comprising the steps of exposing a plurality ofstrands at two belt ends, and applying a vulcanizable rubber compositionto the exposed strands to form a spliced joint between the two beltends, the vulcanizable rubber composition comprising 100 parts by weightof rubber, and the rubber comprising from about 1 to about 40 parts byweight of polyoctenamer.

BACKGROUND OF THE INVENTION

[0002] Conveyor belts are commonly used as a means to move material fromone location to another. In large mining operations, the conveyor beltis generally formed of a rubber body embedded with steel cords orstrands. A cover compound can be used at the surface wherein thematerial is to be conveyed. Generally the compound is very abrasion andcut resistant and of sufficient thickness to prevent the rocks beingconveyed from tearing the belt. A pulley compound can be used on theinterior surface, this rubber is ideally suited for improved wear as thebelt traverses over the pulleys used to drive the belt.

[0003] These steel corded or stranded belts may extend several miles andcost millions of dollars to install and fabricate. The fabrication ofsuch belts occurs initially at a factory wherein steel strands or cordsare arranged in a coplanar relationship parallel to the surface of thebelt so that the belt will exhibit uniform expansion and minimizeweaving as it traverses which can cause belt damage.

[0004] The prior art method of fabricating belts requires the steps ofvulcanizing the rubber belt and winding it onto large spools forshipping to the site. Once the spools of belt are received at the site,the ends must be prepared for splicing by removing the vulcanized rubberfrom the strands over a distance determined to be sufficient to provideenough joint length to make a secure splice.

[0005] Removal of the rubber can be a very time consuming and tedioustask. Often times piano wire is used to peel the vulcanized rubber fromthe strands. In large belts of several feet in width over a hundredstrands must be exposed at each joint end. Once exposed, the strands hadto be cleaned of as much of the vulcanized rubber as possible. Thestrands were then cleaned with solvents such as toluene and then abonding agent was applied comprising a 3:2 mixed solution of “ChemlokNo. 203” and xylene, for example, and rubber cement is applied to thestrands and dried. After the preparation of both ends as described inU.S. Pat. No. 3,487,871 entitled “A METHOD OF JOINING CONVEYOR BELTSHAVING STEEL CORDS EMBEDDED THEREIN” granted Jan. 6, 1970, a joiningmember is formed made of vulcanized or semi-vulcanized rubber of thesame quality as the rubber used in the formation of the belt. The upperface of the member is preferably made of a non-vulcanized rubber andprovided with a plurality of strand receiving grooves. Once the strandsare in place, a bonding agent of the type described above is preferablycoated on the faces of the surfaces to insure complete bonding. Whilethis prior art patent use the term “non-vulcanized rubber” beingpreferable at the melting surfaces of the otherwise vulcanized orsemi-vulcanized member (13), it is believed that the term means “havingat least its upper surface formed of incompletely vulcanized rubber” aswas required in the claim of the patent. An important limitation whenthe member for splicing is semi-vulcanized at this grooved surface, theuse of semi-cured rubber forced the use of bonding solvents. Thesesolvents are high in VOC's and the liberal use of xylene and toluenecreates carcinogenic risks to the personnel. In developed parts of theworld, the use of such solvents is greatly discouraged.

[0006] A second limitation of the prior art splicing member is that themember was apparently molded to the exact width of the belt and hadexactly twice the number of strands as the belt. This meant that foreach belt width, there had to be a unique member since conveyor beltsare not standardized in width or in the size or in the number of strandsto use the concept taught in that patent required specially designedmolds.

[0007] A third limitation of the method of splicing described in U.S.Pat. No. 3,487,871 was that the strands had to be free of any of thevulcanized belt rubber which, if left on the strands, adversely affectedthe bonding.

[0008] An alternative method to solvent stripping method for splicing aconveyor belt is taught in PCT publication WO 00/53952, wherein a methodof splicing the ends of conveyor belts having vulcanized rubber withsteel strands embedded in the vulcanized rubber is disclosed. The methodhas the steps of

[0009] (A) removing a portion of the rubber from the belt ends to bejoined exposing a plurality of strands;

[0010] (B) providing preformed unvulcanized strips of rubber, in anarray of bottom strips each strip having a concave quarter-circularprofile wherein strips when laid adjacently to each other form strandreceiving grooves located on an upper surface,

[0011] (C) placing exposed strands of the belt ends being joined in thegrooves of the bottom strip; and

[0012] (D) placing top strips overlying the array of bottom strips andvulcanizing the strips together thereby forming the spliced joint.

[0013] High modulus compounds have been proven to be necessary toincrease the splice load capability of steel cable-reinforced conveyorbelts. Steel cable-reinforced conveyor belts are graded relative tosplice strength in a dynamic mode. Splice strength has historically beenrated at 30 percent of cable breaking strength. Higher modulus compoundsenable the splice rating to be increased into the 40 to 50 percentrange.

[0014] Steel cable-reinforced conveyor belts are rated according tosplice strength. This rating is determined by dynamically testing a beltunder tension at a percentage of the total belt breaking strength.Customers now refer to this rating for purchasing decisions. It isdesirable to develop novel splice methods utilizing rubber compoundsthat will allow the dynamic testing, commonly referred to as the Hanovertest, to reach a higher number of cycles at a specific test load or abelt to be successfully tested at a higher load.

SUMMARY OF THE INVENTION

[0015] The invention is directed to a method for splicing a conveyorbelt having vulcanized rubber with steel strands embedded in thevulcanized rubber, comprising the steps of exposing a plurality ofstrands at two belt ends, and applying a vulcanizable rubber compositionto the exposed strands to form a spliced joint between the two beltends, the vulcanizable rubber composition comprising 100 parts by weightof rubber, and the rubber comprising from about 1 to about 40 parts byweight of polyoctenamer.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016]FIG. 1 is a fragmentary cross-sectional view of an exemplary beltstructure having steel strands embedded in vulcanized rubber.

[0017]FIG. 2 is a perspective view of a belt end prepared for attachmentto a corresponding belt end and a plurality of the preformedunvulcanized strips (20) of rubber for joint splicing.

[0018]FIG. 3 is a steel cord strand shown sheathed in a coating of thevulcanized belt rubber.

[0019]FIG. 4 is a side elevation view of a vulcanizing press for forminga belt joint in accordance to the invention.

[0020]FIG. 5 is a perspective view of a extruder apparatus for formingthe preformed elastomeric strip.

[0021]FIG. 6 is a cross-sectional view of the extruder die with aprofile for forming the strand receiving grooves in the strip.

[0022]FIG. 7A is a cross-sectional view of a preferred strip (20).

[0023]FIG. 7B is a cross-sectional view of an alternative strip (200).

[0024]FIG. 8 is a cross-sectional view of a preformed strip with a layerof bottom pulley rubber laminated to the strip.

[0025]FIG. 9 is a cross-sectional view of a preformed strip with a layerof top cover rubber laminated to it.

[0026]FIG. 10 is a perspective view of the strip on a spool for splicinga joint for a belt reinforced with steel strands embedded in rubber.

DETAILED DESCRIPTION OF THE INVENTION

[0027] The invention is directed to a method for splicing a conveyorbelt having vulcanized rubber with steel strands embedded in thevulcanized rubber, comprising the steps of exposing a plurality ofstrands at two belt ends, and applying a vulcanizable rubber compositionto the exposed strands to form a spliced joint between the two beltends, the vulcanizable rubber composition comprising 100 parts by weightof rubber, and the rubber comprising from about 5 to about 40 parts byweight of polyoctenamer.

[0028] With reference to FIG. 1, an exemplary conveyor belt (10) will beobserved. The belt (10) has a plurality of steel cords or strands (1)embedded in a core or central layer of rubber (2). As illustrated, thecentral layer (2) is bounded by a bottom layer of rubber (3) of acompound ideally suited for contacting the drive pulleys of the conveyorsystem (not shown) and a cover layer (4) of a rubber compound ideallysuited for abrasion and cut resistance. Additionally, such belts (10)may include additional textile or fabric layers or alternatively areformed utilizing only a single homogeneous rubber without a top orbottom compound while the steel strands of the belt may be impregnatedor coated with a thin rubber bonding layer or sheath (5) to enhance cordadhesion. Nevertheless, the present invention is ideally suite tofacilitate the splicing of almost any known type of rubber conveyorbelts (10) having steel cords or strands (1).

[0029] As shown, preparation of the belt ends (11, 12) to be joined isillustrated in FIG. 2. The belt ends (11, 12) has a portion of the body(14) of the belt (10) removed to expose the steel strands (1). Forconvenience, the term “body (14) of the belt (10)” is intended toinclude all body elements such as the central layer (2), the bottom (3),the cover (4), and any other layers. That portion of the body (14) isremoved preferably across the width of the belt in a diagonallyextending direction. This insures that the splice seam will not approacha drive pulley simultaneously. Additionally the layer of rubber on thetop surface of the strands may be cut back further than the lower layerof rubber below the strands, this method of ends (11, 12) preparation iscommonly referred to as a stepped contour. These features, although notrequired, can improve the splice joint in some applications.

[0030] Once the rubber body (14) is removed from an end (11, 12), thestrands (1) of steel cord are exposed. In some techniques of removingthe rubber body (14) steel piano wire is used to peel the rubber off thecords (1). In that method of body removal (14), virtually all of therubber sheathing the steel cord is removed such that the cords are onlyat least partially sheathed in cured rubber. If desired, the remainingrubber bonded to the cords or strands can be removed by wire brushes orthe like. This technique is quite tedious and time-consuming, however,and is preferably avoided.

[0031] An alternative method of removing the rubber body (14) includesusing a means having contoured cutting surfaces that remove the rubberbody (14) while leaving the strands (1) coated in a thin sheath ofrubber (5) as shown in FIG. 3. In this technique, the strands (1) can bebuffed to enhance the adhesion of the cured rubber sheath (5) prior tosplicing the joint. Thus, in this embodiment part of the vulcanizedrubber in the belt is removed from the strands, and at least part of thevulcanized rubber remains on the strands. The part of the vulcanizedrubber remaining on the strands may be a continuous sheath ordiscontinuous, with some areas of bare strand exposed.

[0032] It is important to note that the present invention is ideallysuited to be used on belts; wherein the strands are exposed at the endof the belts as a result of a technique of manufacture. In such a case,the step of preparing the ends (11, 12) for splicing can be avoided ormodified eliminating the step of removing the cured rubber.

[0033] As shown in FIG. 2, the exposed strands or cords (1) are ideallyplaced in depressions (22A, 22B) in preformed strips (20) ofunvulcanized rubber. These depressions (22A, 22B) each represent aportion of a strand receiving groove (22). Ideally, the number ofgrooves (22) per inch are twice the number of strands per inch at oneend of the belt.

[0034] The preformed strips of unvulcanized rubber include avulcanizable rubber composition. One essential component of thevulcanizable rubber composition is a polyoctenamer. Suitablepolyoctenamer may include cyclic or linear macromolecules based oncyclooctene, or a mixture of such cyclic and linear macromolecules.Suitable polyoctenamer is commercially available as Vestenamer 8012 orV6213 from Degussa AG High Performance Polymers. Vestenamer is apolyoctenamer produced in a methathesis reaction of cyclooctene. In oneembodiment, the octenamer may have a weight averaged molecular weight ofabout 90,000 to about 110,000; a glass transition temperature of fromabout −65° C. to about −75° C.; a crystalline content of from about 10to about 30 percent by weight; a melting point of from about 36° C. toabout 54° C.; a thermal decomposition temperature of from about 250° C.to about 275° C.; a cis/trans ratio of double bonds of from about 20:80to about 40:60; and Mooney viscosity ML 1+4 of less than 10.

[0035] The amount of polyoctenamer used in the vulcanizable rubbercomposition is sufficient to impart a desirable level of adhesion andmodulus. In one embodiment, polyoctenamer is added in an amount rangingfrom about 1 to about 40 percent by weight of the total rubber orelastomer used in the rubber composition, or about 1 to about 40 phr(parts per hundred rubber). For example, 1 to 40 phr polyoctenamer maybe used along with 60 to 99 phr of at least one other elastomer, to makeup 100 parts of rubber or elastomer. Alternatively, from about 5 phr toabout 30 phr polyoctenamer is added to the rubber composition.

[0036] Along with the polyoctenamer, at least one additional, otherelastomer may be present in the rubber composition. The at least oneadditional elastomer may be selected from among elastomersconventionally used in various articles of manufacture. Such elastomersinclude but are not limited to elastomers such as polychloroprene,poly-epichlorohydrin, polyisobutylene, halogenated-polyisobutylene,natural rubber, polyisoprene, polybutadiene, styrene-butadiene, andblends of such elastomers. In one embodiment, the vulcanizable rubbercomposition includes natural rubber and styrene-butadiene rubber.

[0037] In addition to the elastomers in the vulcanizable rubbercomposition, fillers may be also present. The amount of such fillers mayrange from 10 to 250 phr. Preferably, the filler is present in an amountranging from 20 to 100 phr.

[0038] The commonly employed siliceous pigments which may be used in therubber composition include conventional pyrogenic and precipitatedsiliceous pigments (silica), although precipitated silicas arepreferred. The conventional siliceous pigments preferably employed inthis invention are precipitated silicas such as, for example, thoseobtained by the acidification of a soluble silicate, e.g., sodiumsilicate.

[0039] Such conventional silicas might be characterized, for example, byhaving a BET surface area, as measured using nitrogen gas, preferably inthe range of about 40 to about 600, and more usually in a range of about50 to about 300 square meters per gram. The BET method of measuringsurface area is described in the Journal of the American ChemicalSociety, Volume 60. Page 304 (1930).

[0040] The conventional silica may also be typically characterized byhaving a dibutylphthalate (DBP) absorption value in a range of about 100to about 400, and more usually about 150 to about 300.

[0041] The conventional silica might be expected to have an averageultimate particle size, for example, in the range of 0.01 to 0.05 micronas determined by the electron microscope, although the silica particlesmay be even smaller, or possibly larger, in size.

[0042] Various commercially available silicas may be used, such as, onlyfor example herein, and without limitation, silicas commerciallyavailable from PPG Industries under the Hi-Sil trademark withdesignations 210, 243, etc; silicas available from Rhodia, with, forexample, designations of Z1165MP and Z165GR and silicas available fromDegussa AG with, for example, designations VN2 and VN3, etc.

[0043] Commonly employed carbon blacks can be used as a conventionalfiller. Representative examples of such carbon blacks include N110,N121, N220, N231, N234, N242, N293, N299, S315, N326, N330, M332. N339,N343, N347, N351, N358, N375, N539, N550, N582, N630, N642, N650, N683,N754, N762, N765, N774, N787, N907, N908, N990 and N991. These carbonblacks have iodine absorptions ranging from 9 to 145 g/kg and DBP No.ranging from 34 to 150 cm³/100 g.

[0044] It may be preferred to have the vulcanizable rubber compositionfor use in the composite material to additionally contain a conventionalsulfur containing organosilicon compound. Examples of suitable sulfurcontaining organosilicon compounds are of the formula:

Z-Alk-S_(n)-Alk-Z  I

[0045] in which Z is selected from the group consisting of

[0046] where R⁶ is an alkyl group of 1 to 4 carbon atoms, cyclohexyl orphenyl; R⁷ is alkoxy of 1 to 8 carbon atoms, or cycloalkoxy of 5 to 8carbon atoms; Alk is a divalent hydrocarbon of 1 to 18 carbon atoms andn is an integer of 2 to 8.

[0047] Specific examples of sulfur containing organosilicon compoundswhich may be used in accordance with the present invention include:3,3′-bis(trimethoxysilylpropyl) disulfide, 3,3′-bis(triethoxysilylpropyl) disulfide, 3,3′-bis(triethoxysilylpropyl)tetrasulfide, 3,3′-bis(triethoxysilylpropyl) octasulfide,3,3′-bis(trimethoxysilylpropyl) tetrasulfide,2,2′-bis(triethoxysilylethyl) tetrasulfide,3,3′-bis(trimethoxysilylpropyl) trisulfide,3,3′-bis(triethoxysilylpropyl) trisulfide,3,3′-bis(tributoxysilylpropyl) disulfide,3,3′-bis(trimethoxysilylpropyl) hexasulfide,3,3′-bis(trimethoxysilylpropyl) octasulfide,3,3′-bis(trioctoxysilylpropyl) tetrasulfide,3,3′-bis(trihexoxysilylpropyl) disulfide,3,3′-bis(tri-2″-ethylhexoxysilylpropyl) trisulfide,3,3′-bis(triisooctoxysilylpropyl) tetrasulfide,3,3′-bis(tri-t-butoxysilylpropyl) disulfide, 2,2′-bis(methoxy diethoxysilyl ethyl) tetrasulfide, 2,2′-bis(tripropoxysilylethyl) pentasulfide,3,3′-bis(tricyclonexoxysilylpropyl) tetrasulfide,3,3′-bis(tricyclopentoxysilylpropyl) trisulfide,2,2′-bis(tri-2″-methylcyclohexoxysilylethyl) tetrasulfide,bis(trimethoxysilylmethyl) tetrasulfide, 3-methoxy ethoxy propoxysilyl3′-diethoxybutoxy-silylpropyltetrasulfide, 2,2′-bis(dimethylmethoxysilylethyl) disulfide, 2,2′-bis(dimethyl sec.butoxysilylethyl)trisulfide, 3,3′-bis(methyl butylethoxysilylpropyl) tetrasulfide,3,3′-bis(di t-butylmethoxysilylpropyl) tetrasulfide, 2,2′-bis(phenylmethyl methoxysilylethyl) trisulfide, 3,3′-bis(diphenylisopropoxysilylpropyl) tetrasulfide, 3,3′-bis(diphenylcyclohexoxysilylpropyl) disulfide, 3,3′-bis(dimethylethylmercaptosilylpropyl) tetrasulfide, 2,2′-bis(methyldimethoxysilylethyl) trisulfide, 2,2′-bis(methylethoxypropoxysilylethyl) tetrasulfide, 3,3′-bis(diethylmethoxysilylpropyl) tetrasulfide, 3,3′-bis(ethyl di-sec.butoxysilylpropyl) disulfide, 3,3′-bis(propyl diethoxysilylpropyl)disulfide, 3,3′-bis(butyl dimethoxysilylpropyl) trisulfide,3,3′-bis(phenyl dimethoxysilylpropyl) tetrasulfide, 3-phenylethoxybutoxysilyl 3′-trimethoxysilylpropyl tetrasulfide,4,4′-bis(trimethoxysilylbutyl) tetrasulfide,6,6′-bis(triethoxysilylhexyl) tetrasulfide,12,12′-bis(triisopropoxysilyl dodecyl) disulfide,18,18′-bis(trimethoxysilyloctadecyl) tetrasulfide,18,18′-bis(tripropoxysilyloctadecenyl) tetrasulfide,4,4′-bis(trimethoxysilyl-buten-2-yl) tetrasulfide,4,4′-bis(trimethoxysilylcyclohexylene) tetrasulfide,5,5′-bis(dimethoxymethylsilylpentyl) trisulfide,3,3′-bis(trimethoxysilyl-2-methylpropyl) tetrasulfide,3,3′-bis(dimethoxyphenylsilyl-2-methylpropyl) disulfide.

[0048] The preferred sulfur containing organosilicon compounds are the3,3′-bis(trimethoxy or triethoxy silylpropyl) sulfides. The mostpreferred compounds are 3,3′-bis(triethoxysilylpropyl) disulfide and3,3′-bis(triethoxysilylpropyl) tetrasulfide. Therefore as to formula I,preferably Z is

[0049] where R⁷ is an alkoxy of 2 to 4 carbon atoms, with 2 carbon atomsbeing particularly preferred; alk is a divalent hydrocarbon of 2 to 4carbon atoms with 3 carbon atoms being particularly preferred; and n isan integer of from 2 to 5 with 2 and 4 being particularly preferred.

[0050] The amount of the sulfur containing organosilicon compound offormula I in a rubber composition will vary depending on the level ofother additives that are used. Generally speaking, the amount of thecompound of formula I will range from 0.5 to 20 phr. Preferably, theamount will range from 1 to 10 phr.

[0051] It is readily understood by those having skill in the art thatthe vulcanizable rubber composition would be compounded by methodsgenerally known in the rubber compounding art, such as mixing thevarious sulfur-vulcanizable constituent rubbers with various commonlyused additive materials such as, for example, sulfur donors, curingaids, such as activators and retarders and processing additives, such asoils, resins including tackifying resins and plasticizers, fillers,pigments, fatty acid, zinc oxide, waxes, antioxidants and antiozonantsand peptizing agents. As known to those skilled in the art, depending onthe intended use of the vulcanizable and vulcanized material (rubbers),the additives mentioned above are selected and commonly used inconventional amounts. Representative examples of sulfur donors includeelemental sulfur (free sulfur), an amine disulfide, polymericpolysulfide and sulfur olefin adducts. Preferably, the sulfurvulcanizing agent is elemental sulfur. The sulfur vulcanizing agent maybe used in an amount ranging from 0.5 to 8 phr. Typical amounts oftackifier resins, if used, comprise about 0.5 to about 10 phr, usuallyabout 1 to about 5 phr. Typical amounts of processing aids compriseabout 1 to about 50 phr. Such processing aids can include, for example,aromatic, naphthenic, and/or paraffinic processing oils. Typical amountsof antioxidants comprise about 1 to about 5 phr. Representativeantioxidants may be, for example, diphenyl-p-phenylenediamine andothers, such as, for example, those disclosed in the Vanderbilt RubberHandbook (1978), Pages 344 through 346. Typical amounts of antiozonantscomprise about 1 to 5 phr. Typical amounts of fatty acids, if used,which can include stearic acid comprise about 0.5 to about 3 phr.Typical amounts of zinc oxide comprise about 2 to about 10 phr. Typicalamounts of waxes comprise about 1 to about 5 phr. Often microcrystallinewaxes are used. Typical amounts of peptizers comprise about 0.1 to about1 phr. Typical peptizers may be, for example, pentachlorothiophenol anddibenzamidodiphenyl disulfide.

[0052] Accelerators are used to control the time and/or temperaturerequired for vulcanization and to improve the properties of thevulcanizate. In one embodiment, a single accelerator system may be used,i.e., primary accelerator. The primary accelerator(s) may be used intotal amounts ranging from about 0.5 to about 4, preferably about 0.8 toabout 1.5, phr. In another embodiment, combinations of a primary and asecondary accelerator might be used with the secondary accelerator beingused in smaller amounts, such as from about 0.05 to about 3 phr, inorder to activate and to improve the properties of the vulcanizate.Combinations of these accelerators might be expected to produce asynergistic effect on the final properties and are somewhat better thanthose produced by use of either accelerator alone. In addition, delayedaction accelerators may be used which are not affected by normalprocessing temperatures but produce a satisfactory cure at ordinaryvulcanization temperatures. Vulcanization retarders might also be used.Suitable types of accelerators that may be used in the present inventionare amines, disulfides, guanidines, thioureas, thiazoles, thiurams,sulfenamides, dithiocarbamates and xanthates.

[0053] The mixing of the vulcanizable rubber composition can beaccomplished by methods known to those having skill in the rubber mixingart. For example the ingredients are typically mixed in at least twostages, namely at least one non-productive stage followed by aproductive mix stage. The final curatives including sulfur vulcanizingagents are typically mixed in the final stage which is conventionallycalled the “productive” mix stage in which the mixing typically occursat a temperature, or ultimate temperature, lower than the mixtemperature(s) than the preceding non-productive mix stage(s). Therubber and carbon black are mixed in one or more non-productive mixstages. The terms “non-productive” and “productive” mix stages are wellknown to those having skill in the rubber mixing art. The carbon blackmay be added as a separate ingredient or in the form of a masterbatch.The rubber composition containing the carbon black and thesulfur-containing organosilicon compound, if used, may be subjected to athermomechanical mixing step. The thermomechanical mixing step generallycomprises a mechanical working in a mixer or extruder for a period oftime suitable in order to produce a rubber temperature between 140° C.and 190° C. The appropriate duration of the thermomechanical workingvaries as a function of the operating conditions and the volume andnature of the components. For example, the thermomechanical working maybe from 1 to 20 minutes.

[0054] Each preformed strip (20) of rubber splicing comprising thevulcanizable rubber composition has a base having a width (Ws) and a cutto length Ls as shown in FIG. 2. The strips (20) has a top surface (24)intersected by a plurality of grooves portions (22A, 22B) each grooveportion being a portion of either a first side (25) or a second side(26) of the strip.

[0055] By orienting the strips (20) into an array of bottom strips (20)with the grooved portions 22A and 22B of adjacent strips (20) formgrooves (22) adjacent the strands (1), the strands (1) of one end (11)can be placed in every other groove (22) while the strands (1) of theother end (12) fills the grooves (22) remaining to be filled. Theresulting strands (1) from end (11) and those from end (12) form anoverlapping array of strands (1).

[0056] Since the number of strands (1) in the splice joints areapproximately double the number of strands in the rest of the conveyorbelt (10), it is possible to vary the length of the cords or strands (1)in a number of patterned sequences. The principle concept being that acord (1) cut short in end (11) would be adjacent one or two long cords(1) in end (12) and vice-versa. The resultant effect is that the cords'ends do not bend around the drive pulley at a simultaneous occurrencegiving rise to a peak stress. While these splicing techniques are wellknown in the art, it is important to note that they are easily adaptableto the present invention.

[0057] Once the cords or strands (1) are all placed in the grooves (22)in a proper splicing sequence, an array of top strips (20) is placedover the splice opening covering the strands with an array of uncuredrubber strips (20) on both the top and bottom.

[0058] Preferably, the top strips (20) may be grooved similar to thebottom strips (20). Most preferably, the top and bottom strips are thesame in profile and composition.

[0059] Alternatively, the top may simply be a flat sheet of uncuredrubber.

[0060] Dependent on the amount of opening needed for the splice joint,the strip (20) may be provided in a large spool of continuous length, insuch a case, the strips may be trimmed to fit as needed.

[0061] Alternatively, the strips can be sized in terms of length toprovide the optimal splicing length L_(S) for strength and durabilityand no additional trimming or cutting of the strips (20) would berecommended. In this case. the belt manufacture can at least insure thesplice length is sufficient.

[0062] In terms of strip width (W_(S)), an important feature of thesplicing strip is that they are preformed to a base width (W_(S)) thatis generally about equal to the cord (1) spacing as measured at cordcenters. In belts having a width of five feet or more, it can easily beappreciated that the many strips are easier to handle if nested in aplaten or fixture. The splicing operator simply can place as many stripsas are needed to cover the strands and then must trim cut the last stripto substantially match the overall belt width. Ideally, this trimmingsimply requires taking a hot knife or similar cutting element andpassing it through a groove portion (22A or 22B) of the strip (20). Thisprocedure is applicable to both the top and the bottom of the splicejoint.

[0063] Once the uncured strips (20) are positioned and the strandsproperly placed in the grooves (22), the joint area is placed in acuring press (30) as is shown in FIG. 4. Once cured, the splice iscomplete. The advantages of precision and quality control improvementscan be easily appreciated over the more arcane techniques used in theprior art but, in addition to making a superior splice, this method canreduce splicing time by as much as half over current techniques. Whenone considers that as many as a hundred splices may be needed in a largemining belt, a reduction from 8 hours to less than 4 hours to complete asingle splice joint has obvious cost and time savings.

[0064] In FIG. 5, an extruder (100) is shown for forming the preformedelastomeric strip (20). The extruder (100) has a die head (356) thatshapes the strip's profile. A conveyor mechanism (120) can be used toorient and cool the formed strip.

[0065] In FIG. 6, the die head is shown profiled to form depressions orgroove portions (22A and 22B) in the cross-sectional profile of thestrips (20), these groove portions (22A and 22B) form the strandreceiving grooves (22). One extruder with preferably only one die head(356) having the groove forming portions (22A and 22B) can establish theoverall profile of the strip (20) in a variety of sizes by simplyvarying he extrusion speed and tension. The strip (20) itself is formedby forming, cooling and delivering the uncured rubber to a spool (40).As the strip profile is formed, the strip (20) is transferred directlyonto a conveying means (600) to allow the strip to cool.

[0066] Alternatively, the strip (20) can be transferred onto anotherlayer of rubber (3, 4). As shown in FIGS. 8 and 9 respectively, thepreformed strips can be laminated onto a layer of bottom pulley rubber(3) or onto a layer of top cover rubber (4), thus, making specific topstrips (20) and bottom strips (20). In such a case, a duplex extrudercan be used to simultaneously form the two layers as shown in FIG. 5.

[0067] It is believed preferable to transfer the strip (20) onto acarrier member such as liner (50). Most preferably a poly liner (50)

[0068] As shown in FIG. 10, the strip (20) when placed on a liner (50)can be coiled and spooled. Assuming the strip (20) is attached ortransferred onto the liner (50) at the location where it is formed, i.e.at the extruder, then the adhesion to the liner (50) is such that thestrip (20) will be securely fixed to the liner (50). This minimized thepotential for shipping and handling damage. As shown, the length ofstrip (20) on a spool should be equal to the amount needed to make asplice joint.

[0069] Nevertheless, the principles of forming strips (20)advantageously enables the component to be preformed in a green oruncured state. This insures that the strips (20) can be used without thenecessity of using solvents and cements.

[0070] The invention is further illustrated by the followingnon-limiting example.

EXAMPLE I

[0071] This example illustrates the effect of adding polyoctenamer to avulcanizable rubber composition on the physical properties of thecompound, and on the adhesion of the composition to steel cord.

[0072] Four compound samples were prepared as indicated in Table 1. Thesamples were compounded with identical and standard amounts of fillers,sulfur, accelerators, antioxidants, and process aids. TABLE 1 Sample 1 23 SBR 80 70 60 Natural Rubber 20 20 20 Polyoctenamer 0 10 20

[0073] The samples of Table 1 were cured for 35 minutes at 305° F. andtested for physical properties as indicated in Table 2. TABLE 2 ControlSample 1 2 3 Hardness 77 80 84 Tensile strength (psi) 2942 2730 2637Elongation (%) 444 402 368 Modulus 100% (psi) 507 648 723 Modulus 300%(psi) 1848 2021 2099 Tear die C (lbs./in.) 253 250 256

[0074] Adhesion test blocks were prepared from Samples 1 through 3 using8 mm galvanized steel cord. The test blocks were prepared and tested fordynamic adhesion following the procedures of Australia Standard AS 1333,Appendices I and K. Dynamic adhesion was evaluated as cycles to failureat a frequency of 10 cycles/80 seconds with maximum and minimum force of50 and 6 percent of static pullout force, respectively. Dynamic adhesionwas evaluated for test blocks made with pre-coated compound toapproximate performance as a splice. The cord was first cured withSample 1 compound, then stripped to leave a thin layer, buffed and thencured to subject stock. Dynamic adhesion results are given in Table 3.TABLE 3 Dynamic Adhesion Control Sample 1 2 3 Dynamic Adhesion 2561831743 110139 (cycles to failure)

[0075] Significantly, surprisingly and unexpectedly the dynamic adhesionmore than quadrupled for Sample 3 containing 20 parts polyoctenamer, ascompared to Control Sample 1. Sample 2 also showed significantimprovement in dynamic adhesion. Conveyor belt splices utilizingpolyoctenamer as in the present invention may exhibit a dynamic adhesionrating in the splice of more than 50,000 cycles; alternatively, morethan 75,000 cycles; alternatively, more than 100,000 cycles.

[0076] While certain representative embodiments and details have beenshown for the purpose of illustrating the invention, it will be apparentto those skilled in this art that various changes and modifications maybe made therein without departing from the spirit or scope of theinvention.

What is claimed is:
 1. A method of splicing a conveyor belt havingvulcanized rubber with steel strands embedded in the vulcanized rubber,comprising the steps of: (A) exposing a plurality of strands at two beltends; and (B) applying a vulcanizable rubber composition to the exposedstrands to form a spliced joint between the two belt ends, saidvulcanizable rubber composition comprising 100 parts by weight ofrubber, said rubber comprising from about 1 to about 40 parts by weightof polyoctenamer.
 2. The method of claim 1, wherein said vulcanizablerubber composition further comprises at least one additional rubberselected from the group consisting of polychloroprene,poly-epichlorohydrin, polyisobutylene, halogenated-polyisobutylene,natural rubber, polyisoprene, polybutadiene, styrene-butadiene, andblends thereof.
 3. The method of claim 1, wherein said vulcanizablerubber composition further comprises at least one additional rubberselected from styrene-butadiene rubber and natural rubber.
 4. The methodof claim 1, wherein said vulcanizable rubber composition comprises fromabout 5 to about 30 parts by weight of polyoctenamer.
 5. The method ofclaim 1, wherein said step of applying a vulcanizable rubber compositionto said strands comprises the steps of: (A) providing two arrays ofunvulcanized strips of said vulcanizable rubber composition, each stripof rubber having a preformed cross-sectional profiles, one array ofstrips being an array of bottom strips having a plurality ofsubstantially parallel strand receiving grooves located on a first sideor a second side of the strips, the other array of strips being an arrayof top strips; (B) placing the exposed strands of the belt ends beingjoined in the grooves of the one array of bottoms strip; (C) placing thearray of top strips overlying the array of bottom strips; and (D)vulcanizing the strips together and to strands thereby forming thespliced joint.
 6. The method of claim 1, wherein part of said vulcanizedrubber remains on the exposed strands.
 7. The method of claim 1, whereinsaid vulcanizable rubber composition further comprises from about 20 toabout 10 to about 250 parts by weight of a filler selected from carbonblack and silica.
 8. The method of claim 1, wherein said splice jointhas a dynamic adhesion rating of at least 50,000 cycles, based onAS-1333, Appendix K.
 9. The method of claim 1, wherein said splice jointhas a dynamic adhesion rating of at least 75,000 cycles, based onAS-1333, Appendix K.
 10. The method of claim 1, wherein said splicejoint has a dynamic adhesion rating of at least 100,000 cycles, based onAS-1333, Appendix K.
 11. A conveyor belt having at least one splicedjoint comprising a vulcanizable rubber composition comprising 100 partsby weight of rubber, said rubber comprising from about 1 to about 40parts by weight of polyoctenamer.
 12. The conveyor belt of claim 11,wherein said vulcanizable rubber composition further comprises at leastone additional rubber selected from the group consisting ofpolychloroprene, poly-epichlorohydrin, polyisobutylene,halogenated-polyisobutylene, natural rubber, polyisoprene,polybutadiene, styrene-butadiene, and blends thereof.
 13. The conveyorbelt of claim 11 wherein said vulcanizable rubber composition furthercomprises at least one additional rubber selected from styrene-butadienerubber and natural rubber.
 14. The conveyor belt of claim 11, whereinsaid vulcanizable rubber composition comprises from about 5 to about 30parts by weight of polyoctenamer.
 15. The conveyor belt of claim 11,wherein said splice joint has a dynamic adhesion rating of at least50,000 cycles, based on AS-1333, Appendix K.
 16. The conveyor belt ofclaim 11, wherein said splice joint has a dynamic adhesion rating of atleast 75,000 cycles, based on AS-1333, Appendix K.
 17. The conveyor beltof claim 11, wherein said splice joint has a dynamic adhesion rating ofat least 100,000 cycles, based on AS-1333, Appendix K.